Radio communication device and frequency error measurement method

Abstract

A radio communication device includes a transmission unit that performs a radio transmission process on a baseband signal in which transmission data is included and that transmits a signal in which the baseband signal is superimposed on a carrier wave; a feedback unit that feeds back the signal transmitted by the transmission unit; a detecting unit that detects a carrier wave component by removing a component corresponding to the baseband signal from a feedback signal that is fed back by the feedback unit; a counting unit that counts the pulses of the carrier wave component detected by the detecting unit; and a calculating unit that calculates a frequency error of the carrier wave by using a count value obtained by the counting unit.

What is claimed is: 
     
       1. A radio communication device comprising:
 a transmission unit that performs a radio transmission process on a baseband signal in which transmission data is included and that transmits a signal in which the baseband signal is superimposed on a carrier wave; 
 a feedback unit that feeds back the signal transmitted by the transmission unit; 
 a detecting unit that detects a carrier wave component by removing a component corresponding to the baseband signal from a feedback signal that is fed back by the feedback unit; 
 a counting unit that counts pulses of the carrier wave component detected by the detecting unit; and 
 a calculating unit that calculates a frequency error of the carrier wave by using a count value obtained by the counting unit. 
 
     
     
       2. The radio communication device according to  claim 1 , wherein
 the transmission unit includes
 a DA converter that performs digital-to-analogue (DA) conversion on the baseband signal, 
 a modulator that superimposes an analog baseband signal that is obtained by the DA converter on a carrier wave of a radio frequency by using a clock of the baseband signal, and 
 a power amplifier that amplifies a signal output from the modulator, and 
 
 the feedback unit includes
 a converting unit that converts a frequency of the signal amplified by the power amplifier to an intermediate frequency by using the clock of the baseband signal, and 
 an AD converter that performs analogue-to-digital (AD) conversion on the feedback signal converted by the converting unit. 
 
 
     
     
       3. The radio communication device according to  claim 1 , further comprising an estimating unit that derives a prediction line of frequency errors on the basis of the frequency error calculated by the calculating unit and that estimates, by using the prediction line, when the frequency error reaches a predetermined threshold. 
     
     
       4. The radio communication device according to  claim 1 , wherein the calculating unit calculates the frequency error of the carrier wave by using the count value obtained during measurement time measured on the basis of time information that is acquired from outside. 
     
     
       5. A radio communication system comprising:
 a signal processing unit; and 
 a plurality of radio communication devices connected to the signal processing unit, wherein 
 each of the radio communication devices includes
 a transmission unit that performs a radio transmission process on a baseband signal in which transmission data received from the signal processing unit is included and that transmits a signal in which the baseband signal is superimposed on a carrier wave, 
 a feedback unit that feeds back the signal transmitted by the transmission unit, 
 a detecting unit that detects a carrier wave component by removing a component corresponding to the baseband signal from a feedback signal that is fed back by the feedback unit, and 
 a counting unit that counts pulses of the carrier wave component detected by the detecting unit, and 
 
 the signal processing unit
 receives a count value obtained by the counting unit from the plurality of the radio communication devices, 
 calculates a frequency error of the carrier wave by using the received count value, and 
 when frequency errors calculated for the plurality of radio communication devices indicate similar tendencies, determines that the signal processing unit is abnormal. 
 
 
     
     
       6. A frequency error measurement method comprising:
 performing a radio transmission process on a baseband signal in which transmission data is included and transmitting a signal in which the baseband signal is superimposed on a carrier wave; 
 feeding back the transmitted signal; 
 detecting a carrier wave component by removing a component corresponding to the baseband signal from a feedback signal that is fed back; 
 counting pulses of the detected carrier wave component; and 
 calculating a frequency error of the carrier wave by using a count value obtained at the counting.